On Thanksgiving Day in 1915, a 36-year-old physicist named Albert Einstein submitted a paper to the Proceedings of the Prussian Academy of Sciences in Berlin. That paper — titled "Die Feldgleichungen der Gravitation," or "The Field Equations of Gravity" — was a scientific blockbuster, unveiling equations that govern the universe.
Einstein was in Germany at the time, so the U.S. holiday of Thanksgiving may not have been top of mind. (Also, he was probably a bit distracted by revolutionizing modern physics and astronomy.) Yet even if Einstein wasn't thinking of Thanksgiving on that fateful November day, it was one of many moments in his life that would inspire gratitude from people around the world, even a century later.
Physicists and astronomers are understandably thankful for Einstein's work, as are many other scientists whose careers hinge on his game-changing equations. But Einstein isn't just an esoteric hero for scholars — he's one of the most famous scientists of all time, serving as a global icon and synonym for ingenuity itself.
Hyperbole is common when describing the impact of historical figures, yet in Einstein's case, the superlatives are generally apt. He really was a rare genius who transformed our understanding of space, time and gravity, and his discoveries really did enable a wide array of modern technology. He also left a rich cultural legacy, proving the power of daydreams and independent thought, among other things.
So, in the seasonal spirit of thankfulness — or just because gratitude is good for you any time of year — here are a few brief reasons to appreciate Einstein:
That 1915 paper outlined Einstein's general theory of relativity — "one of the towering achievements of 20th-century physics," writes University of Oxford astrophysicist Pedro Ferreria, because it revealed that gravity is a curvature of spacetime caused by matter. This built on Einstein's special theory of relativity, and the two collectively form a sweeping explanation for how the universe works.
Not only is Einstein's relativity fascinating, but it has had major implications for scientists, such as astronomers who plan space missions, measure the mass of stars or study gravitational waves. And while it may seem fairly abstract and arcane for the rest of us, relativity affects daily life more than we tend to realize.
It's a big deal for satellite navigation systems, for example, like the the U.S. Global Positioning System (GPS). That's because GPS and similar units pinpoint their location on Earth by communicating with an array of satellites, which are moving through medium-Earth orbit at roughly 14,000 kph (8,700 mph). Since that's faster than our speed on the ground, special relativity tells us those satellites will experience a slower passage of time than we do. Known as time dilation, this should cause the satellites' clocks to fall behind earthly clocks by about 7 microseconds per day.
On the other hand, general relativity predicts that time will seem to slow down near massive objects like Earth, due to the increased curvature of spacetime. And because GPS satellites are located about 20,000 kilometers (12,000 miles) above the planet's surface — where spacetime is less curved — this effectively speeds up their clocks. As Ohio State University astronomer Richard Pogge explains, the combination of these two relativistic effects means that an atomic clock on a GPS satellite should outpace an identical clock on Earth by about 38 microseconds per day.
That may not sound like much, but if satellite-navigation systems didn't account for this effect, global positioning errors would accumulate at a rate of about 10 km (6.2 miles) per day. Thankfully, Einstein's theories of relativity predicted this potential problem, so our satnav systems are designed to compensate for it.
Molecules and stock investing
1905 was a big year for Einstein, who completed his Ph.D. thesis, published his special theory of relativity and described how light exists in packets of energy, an idea that eventually won him a Nobel Prize. He also performed less famous feats, such as his explanation for a phenomenon called "Brownian motion."
Described in 1820 by botanist Robert Brown, Brownian motion is the jittery movement of tiny observable particles suspended in a fluid. This effect had long defied explanation, but in 1905, Einstein used statistics to provide an answer. Molecules in a liquid should experience tiny fluctuations, he argued, in which random molecules occasionally deviate from their average behavior. A cluster of molecules in a liquid would briefly move together in the same direction, causing a larger, observable particle in the liquid to budge slightly with them. Another group of molecules would then push in a different direction, resulting in a zig-zag.
Einstein even calculated the average horizontal distance a particle would move within a liquid in a given amount of time. Beyond explaining Brownian motion, this offered a blueprint for finally verifying the existence of molecules. And that's what French scientist Jean Perrin did in 1908, building on Einstein's estimate in research that later won Perrin a Nobel Prize. But on top of shedding light on molecules, Einstein's work also helped establish the role of probability in physics — "a defining moment in the philosophy of science," according to physicist Cormac O'Raifeartaigh.
"Today, Einstein's notion of statistical fluctuations has found application throughout the sciences," writes O'Raifeartaigh, a lecturer at the Waterford Institute of Technology in Ireland. "From the study of cell membranes to our view of evolution, from the analysis of weather systems to the study of the stock market, it underpins our understanding of all complex systems."
Cellphones and solar cells
Solar panels reflect a sunset and mountains in Southern California. (Photo: Thomas Galvez [CC BY 2.0]/Flickr)
When Einstein won the Nobel Prize in physics, the award was meant to honor "his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect." That refers to a phenomenon in which light, when shined with enough energy on certain materials, triggers the emission of electrons. Scientists had known about the photoelectric effect for years, but as astrophysicist Sabrina Stierwalt writes, it couldn't be explained under the traditional concept of light as a wave.
It could be explained, however, by thinking of light as a stream of particles, or "quanta." That's what Einstein did in 1905, showing that these quanta of light — now called photons — could transfer enough energy to a metal surface to produce the previously unexplained photoelectric effect. This principle is key to solar cells, but it's also important for an extremely wide range of modern electronics.
As NBC News noted in 2005 for the 100th anniversary of this milestone, "Einstein's identifying of photons underlay the development of many of the advanced electronic inventions of the 20th century. It was the statement of the quantum effect, without which we would not have cellular telephones or smoke detectors or burglar alarms or those doors that automatically open at the supermarket or on the elevator."
In a 1917 paper, Einstein paved the way for lasers by introducing the possibility of a process called stimulated emission. "A splendid light has dawned on me about the absorption and emission of radiation," he wrote in a letter to a friend months earlier.
When an atom is in an "excited" state, meaning it has higher energy than its ground state, it may spontaneously drop to a lower energy level, releasing photons in a process known as spontaneous emission. As Einstein argued, this process can also be stimulated by incoming photons, which cause the emitted photons to travel in the same direction as the incoming light (rather than randomly), effectively amplifying the incoming radiation to create a narrow, focused beam of coherent light.
Decades later, Einstein's process of stimulated emission allowed other scientists to develop the first laser (a name that originated as an acronym for "Light Amplification by Stimulated Emission of Radiation"). Einstein may not have invented the laser, but he provided crucial groundwork for technology that's now used in a variety of ways, from science, medicine and telecommunications to consumer electronics.
Daydreams and disruption
The secret behind many of Einstein's scientific breakthroughs was his uncanny knack for daydreaming. It famously got him in trouble in school as a child, although he later enrolled in a Swiss village school that encouraged visual imagination from students. That's where he tried to imagine himself traveling fast enough to catch up with a beam of light, a daydream that eventually led him to develop his transformative special theory of relativity. His general theory of relativity, which came a decade later, also grew from the seed of a daydream about a person in free-fall.
He called that "the happiest thought of my life," notes biographer Walter Isaacson. "Einstein relished what he called Gedankenexperimente, ideas that he twirled around in his head rather than in a lab," Isaacson wrote in 2015. "As these thought experiments remind us, creativity is based on imagination. If we hope to inspire kids to love science, we need to do more than drill them in math and memorized formulas. We should stimulate their minds' eyes as well. Even let them daydream."
Research has since validated Einstein's approach, showing that daydreaming can offer a wealth of benefits, such as improving mental performance on complex tasks, boosting creativity, encouraging epiphanies, reducing stress and strengthening memory. That's a big reason why he has become such a salient role model not just for aspiring physicists, but for almost anyone who can appreciate the power of an idea. Einstein proved that conventional wisdom isn't always as wise as it seems, and that a daydream isn't necessarily an indulgent flight of fancy.
As Einstein himself once said, "Imagination is more important than knowledge."
Whimsy and wonder
Einstein lived at a pivotal time for science, and aside from his many discoveries, he helped people reimagine how a "genius" looks and acts. He was a new kind of celebrity scientist, and his irreverent style and distaste for conformity came to be symbolized by his famously wild hair, as philosopher Steven Gimbel wrote in 2015.
"On the one hand, Einstein is the very icon of the genius, someone whose innate intelligence made him radically unlike the masses. But in allowing his hair to become the spectacle it was, he became a symbol that said that special people can come from anywhere, can look like anyone," Gimbel wrote. "Einstein, with his wild hair, signaled that human advancement comes not from the conformity the authorities demand, but from difference."
Not only did Einstein help restore public faith in the power of reason and intellect, but he showed that brilliant scientists don't have to be stodgy, either in terms of style or substance. "It is important for the common good to foster individuality: for only the individual can produce the new ideas which the community needs for its continuous improvement and requirements," Einstein said at a dinner in 1952.
Of course, the bulk of Einstein's legacy comes from his breakthroughs in physics, which have enabled or improved a wide array of modern technologies. There are more reasons to be thankful for Einstein than the ones listed here, but one of his greatest gifts to society is the way he inspired us to embrace curiosity and awe.
"The fairest thing we can experience is the mysterious," Einstein wrote in "The World As I See It" in 1949. "It is the fundamental emotion which stands at the cradle of true art and true science. He who knows it not and can no longer wonder, no longer feel amazement, is as good as dead, a snuffed-out candle."